Method and apparatus for recording and reproducing sound



Filed Feb. 13, 1955 2 Sheets-Sheet l "gm LOUD g: 2 SPEAKER AMPLIFIER ,32 f INVENTOR 5 E l D i o 22 faul Safransfm D E 2 BY p D EC, n 22D%//,a1y,%$-bm e: in: o Efcs ATTORNEYS METHOD AND APPARATUS FOR RECORDINGAND REPRODUCING SOUND Filed Feb. 13,. 1933 2 Sheets-Sheet 2 ATTORNEYSPaul fiafran "in; BY 0 Patented Apr. 21, 1936 UNITED STATES PATENTOFFICE METHOD AND APARATUS FOR RECORDING AND REPRODUCING SOUND PaulSafranski, New

York, N. Y., assignor to 17 Claims.

This invention deals with the photographic recording of sound and. withthe reproduction of sound from a photographic film record thereof.

One of the objects of this invention is to provide a practical andthoroughly dependable method and apparatus for recording sound on a filmand for reproducing photographic records of sound. Another object is toprovide a method and apparatus of the above-mentioned character in whichthe efficiency of heretofore known methods and apparatus is greatlyincreased, in which substantial and far-reaching economies in energyconsumption may be inexpensively effected, and in which uniformity ofintensity of lo sound over the necessary wide range of frequencies maybe dependably achieved.

Another object is to provide a method and apparatus of theabove-mentioned nature in which costs of operation and maintenance aregreatly decreased and in which the high operating skill, necessary inthe satisfactory maintenance and operation of heretofore knownapparatus, may be successfully dispensed with. Another object is toprovide a method and apparatus of the above-mentioned character in whichcritical adjustments and critically sensitive devices or parts aredispensed with, and to provide, particularly as to the apparatus forsound reproduction an apparatus of high economy of operation and sosimple in construction and control that it is virtually fool-proof andvirtually ideally suited for use in homes, schools, and the like,

Where its operation and control must necessarily be by unskilledoperators.

35 Another object is to provide a method and apparatus for soundreproduction that lends itself readily to low cost of production and tolow cost of maintenance. Another object is to provide a soundreproducing method and apparatus 40 that will respond to and reproduce,with substantial uniformity, frequencies over such a wide range thatdefects, such as are present in present-day apparatus, in the ultimatesound, are eliminated and thus naturalness or virtually perfectreproduction achieved. It is in particular an object of this inventionto provide a sound reproducing system of this last-mentioned characterfor use in large auditoriums, such as theatres, halls, or the like,where the intensity or volume of sound must necessarily be very greatand where,

because of such magnitude of volume, apparently slight imperfections aremagnified and more easily detectable.

Another object is to provide a system and apparatus for soundreproduction in which the output of the photoelectric cell or otherlight-sensitive device per unit of light input (at the initial source oflight) is high, and thereby to lessen energy consumption, diminish theamplification necessary, and insure longer life and low cost ofoperation.

Another object of this invention is to provide a light or optical systemto which the film record and the light-sensitive or photoelectric cellmay be subjected that will maintain substantial uniformity of frequencyresponse over ranges on the order of from 55 cycles per second to orabove 8000 cycles per second. Another object is to provide a soundreproducing method and apparatus in which sound-frequency-components ofvery low and of very high frequencies are faithfully reproduced and thusthe true quality or naturalness of the recorded sound reproduced.

Another object of this invention is to provide a method and apparatus ofthe above-mentioned character in which the many undesirable anddetrimental factors inherent in present-day apparatus of this charactermay be successfully eliminated; among these factors may be mentioned theexpense of construction and maintenance of the slit through which thelight is made to impinge upon the film, the precision and accuracy ofadjustment of the slit and the maintenance of this adjustment, thedifiiculty and necessity of keeping this extremely minute slit clean andfree from foreign matter, moisture, oil, oil vapors, and the like, thesensitiveness of adjustment of the component parts of the opticalsystem, the low efficiency, the high cost of supervision andmaintenance, the high energy consumption, and like factors. Otherobjects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, arrangements of parts and in the several stepsand relation and order of each of the same to one or more of the others,all as will be illustratively described herein, and the scope of theapplication of which will be indicated inthe following claims.

In the accompanying drawings, in which are shown, by way ofillustration, several possible embodiments of certain of the mechanicalfeatures of my invention,

Figure 1 is a side elevation of the assembled apparatus for soundreproduction;

Figure 2 is a vertical cylindrical sectional view on an enlarged scaleof what may be termed the optical system of the apparatus of Figure 1;

Figure 3 is a vertical transverse sectional view as seen on the line 33of Figure 2;

Figure 4 is a schematic or diagrammatic plan View of the apparatus ofFigure 1, certain additional parts being indicated diagrammatically;

Figure 5 is a fragmentary portion of a standard motion picture filmshowing diagrammatically the sound track thereon with one kind or typeof sound recording;

Figure 6 is a plan view of a fragment of standard motion picture filmshowing diagrammatically the sound track thereon with another kind ortype of sound recording;

Figure '7 is a side elevation, as seen from the left, on an enlargedscale of the photoelectric cell of Figures 1 and 4;

Figure 8 is a perspective view of a light ray controlling element of theoptical system; Figure 8a is a top plan view thereof; Figure 8b is afront elevation thereof; Figure 8c is an end elevation as seen from theleft of Figure 8b, and Figure 8d is a central horizontal sectional viewas seen on the line 8d8d of Figure 82).

Figure 9a is a top plan view, and Figure 9b is a front elevation of amodified form of light ray controlling element, and Figure 9c is an endelevation thereof as seen from the left of Figure 92);

Figure 10a is a front elevation, and Figure 10b is a top plan view ofanother modified form of light ray controlling element, and Figure is anend elevation as seen from the left of Figure 10a;

Figure 11 is a perspective view of another form of light ray controllingelement, and Figure 11a is a top plan view thereof, Figure 111) being afront elevation thereof, and Figure being a side elevation as viewedfrom the left in Figure 111); and

Figure 12 is a diagrammatic representation of a possible form of soundrecording system and apparatus embodying my invention.

Similar reference characters refer to similar parts throughout theseveral views of the drawmgs.

As conducive to a clearer understanding of certain features of myinvention, I wish first to point out that I may first produce, in anysuitable manner, a sound record on a photographic film and in Figures 5and 6 I have shown fragments of motion picture films with sound tracksand sound records thereon of a character now in practical use. Referringfirst to Figure 5, I have shown a section of motion picture film l0preferably of standard size and provided with socalled frames H on whichappear the scene or scenes that have been photographed and alongside ofthe frames I I is a relatively narrow band portion called the soundtrack; this portion or sound track is indicated at [2 and in practice isabout one-eighth of an inch in width. The film I0 is provided with theusual apertures l3 to coact with the teeth of suitable sprocket wheelsand the like for running the film for motion picture projection andsound reproducing purposes.

The sound track l2 of Figure 5 bears, as is diagrammatically indicatedin that figure, the sound record which, with the system of soundrecording that results in this kind of sound record, consists ofso-called lines extending transversely of the sound track, all of thesame length, but of variable or varying density, the density varying ineffect with the variation in frequency of the recorded sound. Thisvarying density is indicated in Figure 5 by the varying shading of thesetransverse lines. A beam of light, projected through the sound track asthe film is moved in the direction of its length, thus varies inintensity at an audio frequency rate and more particularly in accordancewith the frequency of the sound that is recorded on the sound track.

In Figure 6 I have shown diagrammatically the same film ill but with asound track i4, also of a width of about one-eighth of an inch, bearinga sound record in which the light-passing quality of those portions ofthe film bearing the sound record is constant but an audio frequencyvariation in the amount of light passed through the entire sound trackis achieved by varying, at the audio frequency rate, the width of theactual sound record; this is clearly indicated on the sound track M ofthe. film H) of Figure 6.

The method and apparatus for sound reproduction of my invention areparticularly adapted for the translation of sound records like thoseabove described into sound, and accordingly I provide an arrangement forguiding and moving the film [0 (Figure 1) the latter being movedpreferably at a constant rate of speed.

Any suitable form of guiding arrangement or so-called film gate may beemployed for fixing the path of movement of the film I!) as the latteris moved, preferably in a downward direction, between and over thesprocket wheels l5 and 16 which may be driven in any suitable manner andat the desired speed and intended uniform rate; where my apparatus isassociated with a motion picture projecting machine, the drivingmechanism l5l6 may be actuated in any suitable manner from the apparatusthat moves the film for projecting purposes, suitable 1 provision beingmade to achieve continuity of movement of the film I0 along theabove-mentioned path as distinguished from the intermittent movement ofthe film for picture projecting purposes. The film gate or guide isgenerally indicated in Figure 1 at 17 and it serves, as above noted, tofix the plane in which that portion of the film ID that is between thesprockets l5l 6 moves; the film gate l! is provided with a suitableaperture l8 of substantial dimensions so as not to obstruct or interferewith the beam of light that is to be passed through the sound track ofthe moving film.

To the right of the thus-apertured film gate or guide I! is positionedand suitably mounted a suitable light-sensitive device preferably takingthe form of a photoelectric cell generally indicated in Figure l at 19.The photoelectric cell includes a suitable glass envelope in which aremounted the electrodes; the electrodes include a plate member 29 ofsuitably treated sheet metal which is given the shape, as is bettershown in Figure 4, of a half cylinder and positioned substantially atits axis is the coacting electrode in the form of a smaller-diameteredrod or cylinder 2| (Figures 1 and 4). These electrodes are supported inany suitable manner and are connected to terminal conductors 22 and 23in any suitable way. The concave face of the electrode 20 faces towardthe film guide I! and its midpoint, as viewed from the left in Figure 1,is substantially on the optical axis AA with respect to which also thesound track on the film I0 is centered.

The plate 20 of the cell I9 is thus positioned in the path of the beamof light, more clearly hereinafter described, that passes through thesound track of the film l0 and emerges through the large apertures it bywhich the beam is not affected; the intensity of the light beam, itmight at this point be noted, is varied by the sound record on the filmH] (see the sound track l2 or the sound track M of Figures 5 and 6,respectively) and thus the intensity or quantity of light striking thelight-sensitive electrode is varied so as to in turn vary the electricalconductivity of the cell l9, thus to achieve in the output circuit ofthe latter a corresponding audio frequency current.

In Figure 4 the output circuit of the cell I9 is diagrammaticallyrepresented and it includes a suitable source of current 24 of suitablepotential, a suitable amplifier, preferably of the thermionic type,generally indicated at 25. Thus, the energy in the output circuit inwhich the cell I9 is included is amplified and the output of theamplifier 25 is in turn fed to a suitable translating device, such as aloud speaker 26 indicated diagrammatically in Figure 4. The loud speaker26 may be of any suitable form or construction. Where the apparatus isintended to be used in large auditoriums, such as motion picturetheatres, for example, the volume of the sound ultimately produced bythe loud speaker 26 is substantial in magnitude and, if naturalness andtrue quality of the recorded sound are to be achieved, the amplifiermust have supplied to it, by the circuit of the photoelectric cell l9,audio frequency currents which must be made up of the same frequencycomponents recorded on the film and these components must, in intensity,be of magnitudes corresponding, without variation as frequency changes,to the respective magnitudes thereof recorded on the film.

The film guiding and driving mechanism and the support for thephotoelectric cell I9, referring now to Figure 1, may be related in anysuitable manner to a suitable frame or support, a portion of which isshown at 21; part 21 may be considered as part of a motion pictureprojecting machine. At the left-hand end of the frame or support 21 Iprovide a socket 28 for the reception of a lamp bulb 29 of theincandescent filament type, which I prefer to use as a source of light.The socket 28 is preferably adjustably mounted in any suitable waypreferably so that different styles or types of bulbs may be morereadily related to the optical systern and remaining parts. Theadjustable mounting of the socket 28 may be of any desired character andby way of illustration I have shown the socket 28 mounted to be capableof adjustment in three directions, namely, vertically, horizontally (tothe left or right as viewed in Figure 1) and horizontally but at 90 tothe justmentioned horizontal adjustment.

Thus, the socket 213 may be carried on an arm 36 slidably supported in ablock 3|, movement of the socket Z8 and the arm 30 to the left or rightbeing controlled by a suitable thumb nut 32.

The block 3 I, however, is slidably supported on an upstanding post 33and it may be raised or lowered along the post 33 by the thumb nut 34,thus to raise or lower the lamp 29.

The post 33 is supported in a slide 35 guided in ways 36 carried by theframe 21, the ways 36 extending at right angles to the plane of thesheet on which Figure 1 appears, thus to permit the lamp 29 to be movedtoward or away from the observer viewing Figure 1. An adjusting screw 35controls the position of slide 25.

The frame 21 is provided with an upstanding post 3 positionedintermediate of the lamp 29 and the path of the film l0, and post 31 isprovided with a split clamping collar 38, the clamping action of whichis controlled by the clamping screw 39. The clamping collar 38 supportsthe housing 40, preferably tubular in cross-section (with which thelight ray controlling elements and lens or lenses are related and inwhich they are preferably sealed against moisture, vapors, foreignmatter, and the like. The housing 40, moreover, is held by thesupporting post 31 so that the axis of the tube 49 coincides virtuallywith the optical axis A-A above-mentioned and along which the soundtrack and the electrode 26 of the light-sensitive cell are alined.

Before considering in detail the light ray controlling elements relatedto the housing 43, it might first be pointed out that the lamp socket28, with a lamp bulb 29 therein, is adjusted so that the center of theluminous mass of the filament at least approximately coincides with theoptical axis AA and so that that center is spaced to the left of thehousing 48 by a certain approximate distance. This coincidence and thisdistance need not be absolute; that is to say, though there is apreferred or optimum relation for a given incandescent filament bulb andhence a given position for the socket 28, both of which may be achievedby the adjustments of the lamp socket 23 as above described, relativelywide departures from this optimum position or distance are permissible,as will be pointed out in detail hereinafter. Suffice it at this pointto note that a given adjustment for a given lamp bulb of one type willsufiice once and for all for subsequent lamps of the same type, theoptical system forming part of my invention taking care of even therelatively wide variations in dimensions and shape of bulbs of a giventype and intended to be uniform or standard throughout. In fact, farwider departures than just these manufacturing tolerances arepermissible with the apparatus of my invention without requiringreadjustment of the lamp bulb each time.

I might also note at this point that the shape, dimensions,configuration and structure of the filament itself may vary throughoutvery wide limits without affecting the performance of the system andapparatus. For example, it is not vital that a filament of carefullydimensioned rectilinear shape be employed as has heretofore beenproposed in order to obtain a cross-section of beam at the intersectionthereof with the sound track that is or approximates a straight line andis of minute thickness; the filament can be in the form of a ribbonextending generally parallel to one of the sound marks on the soundtrack (see Figures 5 and 6), or the filament may be a helix whose axisis thus substantially parallel to one of the sound record elements onthe sound track, or the filament might be in the shape of an inverted Vthe plane of which extends at right angles to the optical axis A-A, orthe filament might be of the concentrated filament type wherein, to allintents and purposes, the incandescent filament represents and virtuallyis equivalent to an enlarged point or sphere-like mass of light; theseare several of the various possible forms or shapes of filament which,due to certain other features of my invention, I am enabled to employ.

Referring now to Figure 2 I have there shown on an enlarged scale thetubular housing 40 above-mentioned in connection with Figure 1. Theleft-hand end of the tube 1E which illustratively has an inside diameterof approximately 0.75", is counter-bored and threaded as at w in orderthat a disk-like element X may be fitted into that end of the tube 4!!and abutted against the shoulder 46 element X being held in place by acollar 4| threaded into the threaded counterbore 40 Interposed, however,between the element X and the collar 4| is a ring as and a plain glassdisk-like window 43, the parts being sealed, in a manner hereinafterdescribed, so as to exclude from access to the element X foreign matter,moisture, cil, vapors, and the like.

In so far as element X is concerned, it may assume various possibleforms of which one form is shown in perspective in Figure 8.

Referring therefore to Figure 8, element X is made of glass,illustratively of crown glass having an average index of refraction of1.52 and a dispersion factor for the D-line of 64.0 and is of a diameteradequate to be snugly received within the counter-bored portion 41% ofthe tube 40 (see Figure 2); this diameter may be on the order of On itsright-hand face, as viewed in Figures 2, 8, and 8c, the element X isconcaved to provide a cylindrical surface M the axis of which extendsparallel to an element of the sound record (see Figures 5 and 6) andcrosswise of the axis A-A (Figures 1 and 4). The radius of curvature ofthe cylindrical surface 54 is 0.125.

The left-hand face of element X, as viewed in Figures 2, 8, and 8c, ispreferably curved and preferably is given the shape of a portion of acylinder, the axis of which, however, extends 90 to the axis of thecylindrical surface 4 that is, referring to Figure 8, if the axis ofcylindrical surface be considered as extending horizontally (inperspective), the axis of the cylindrical surface 55 is vertical. Thisrelation appears more clearly from a consideration of Figures 8a, 8b,8c, and 811. Its radius of curvature is 0.75".

On the right-hand face of element X (Figures 8 and 80) there remainsegmental areas 45 and ll which are preferably though not necessarilycovered with any suitable opaque material, conveniently by paintingthese surfaces with any suitable opaque paint, varnish, shellac, or thelike.

The action of the element X will be described in detail hereinafter.

At the right-hand end of tube 48 (see Figure .2), the tube is interiorlythreaded as at iil to receive an extension member 38 which exteriorlyappears substantially conical but which interiorly is virtually anextension along the optical axis A-A of the tubular housing 4-3. Theparts 48 and are interconnected by threads and sealed as hereinafterdescribed.

The member at is bored out to provide cylindrical interiors 18 and 48 ofprogressively smaller diameters and supports a suitable lens or lenseswhich preferably take the form of achromatic: doublets.

Thus, a composite lens its-53 is seated in the cylindrical interiorportion 48 and is held up against the right-hand shouldered end thereofby a ring 5i threaded into the part W and with the lens 49-50 sealed, ashereinafter described, to the part 18.

Seated against the left-hand shouldered end of the smaller cylindricalportion 43 is a composite lens 53-54, also sealed to the part andinterlocked with the latter by spinning the edge 48 thereof over theright-hand face of the component lens 54.

The foremost or front achromatic lens 53-54 is made of flint glasshaving an average index of refraction of 1.52 and a dispersion factorfor the D-line of'36.5. Its components are shaped as followsz-Component53 is a double convex lens whose surfaces have radii of curvature of 6mm. the component 54 is double concave and its lefthand face (Figure 2)has a radius of curvature of 6 mm. and its right-hand or front face hasa radius of curvature of 17.5 mm.

Achromatic lens 49-59 is made of similar flint giass and its componentsare as follows:-Lens component 43 is a double convex lens having aradius of curvature for both of its faces of 9 111111.; lens component50 is a piano-concave lens whose left-hand face has a radius ofcurvature of 9 mm. and whose right-hand face is plane. The diameter oflens 49-50 is A" and the diameter of lens 53-54 is 1 5", the diametersof the parts 48 and 68 of the member 48 being correspondinglyproportioned in order snugly to receive the respective lenses.

Intermediate of the ends of the tubular ma. ber 45 (Figure 2) is mounteda diaphragm 55 which, like the various above-mentioned threaded members,may be made of metal; the diaphragm 55 is suitably fixed within the tubell and it has a centrally positioned aperture 55 (see also Figure 3)which is square, being, with respect to the above-mentioned dimensions,in length per side.

The above-described parts thus related to the tubular housing 68 arerelated to the lamp bulb and to the film Ill and to the photoelectriccell !3 as is diagrammatically or schematically shown in 4 but, withrespect to the dimensions above set forth, the following relationsshould be borne in mind:-

The distance 3 (Figure 4) from the filament ze of the lamp bulb 29 tothe left-hand or rear face of the element X, where the filament '29 isillustratively a helix which is 0.375 in length and having an outsidediameter of is approximately 1.25.

The distance C from the right-hand face of lens 53-54 to the right-handface of element X is 2.875".

The distance D from the right-hand face of lens 53-55 to the diaphragm55 is A The lenses 49-59 and 55-54 are relatively close together,approximately A and with a spacing (Figure 4) between the righ -handface of lens 53-54 and the film Ii] of 0.375, film iii and hence thesound track lie at the focus of the objective lens system which theselenses form.

The distance F between the plane of the film iii and the vertical axisof the half--cylindrical plate 23 (where the latter has a radius of0.375) is approximately 1.625.

I have above set forth somewhat in detail the physical dimensions andcharacteristics of the various parts of an illustrative embodiment ofsound reproducing apparatus in order that their construction and actionmay be more readily carried out in practice, but it is to be understoodthat I do not desire or intend to be limited or restricted to thesesomewhat detailed structural relations. As for the action of the systemand apparatus, I direct attention to the following:- Ii have hereinaboveset forth by way of illustration various shapes and structures which thefilament 29 of the lamp 129 of Figure 4 may assume; virtually, no matterwhat the shape of the initial or immediate source of light, the elementX, when shaped substantially as described above, has the property of sorefracting, reflecting, or otherwise affecting or controlling the lightcylindrical surf ace rays emanating from that source as to Vastlyelongate its shape in the direction of the axis of the cylindricalsurface A l (Figures 2 or 8) on its right-hand or front face and todiminish, and to make uniform throughout this elongation, the verticaldimension thereof. For example, if the filament were concentrated ormade short so that it represented virtually a disk of luminosity orincandescence or light of a diameter, let us say of a s" or element X,treating that disklike part as an object, transforms it into atramversely elongated and vertically condensed concentration of light,thus forming virtually a secondary light source; moreover, though theshape of the initial luminous object was irregular or circular, thesecondary source of light which ele ment X forms out of it, as justdescribed, is virtually of uniform vertical dimension as that secondarysource is viewed along the optical axis AA from the right toward theleft (Figures 1, 2 or l). Illustratively, this concentration of lightrays thus effected by the element X and when thus viewed extendsentirely across the cylindrical face 44 along an element thereof andhence parallel to the axis thereof, and its vertical dimension is veryminute, being on the order of ea or less, depending upon the distance Bof Figure 4.

So effective is theaction of element X that, if filament 29 of the lampbulb 29 is V-shaped with the plane of the filament extendingtransversely of the axis A-A, element X nevertheless so controls andaffects the light rays emanating therefrom that the decrease in verticaldimension of the V of the filament and its elongation transversely aresuch that it is virtually impossible to discern from an examination ofthe thus-formed secondary source of light that the primary source oflight actually is V-shaped.

The curvature of the cylindrical face 45 of the element X is such as toprevent a too great elongation in a direction parallel to the axis ofthe M in order thus to insure a high intensity of light per unit area ofshape of the secondary li 'it source thus formed.

In any case, there is thus presented to the projecting lenses ii--53 and53-5 5 and to the diaphragm 55 positioned in advance of the projectinglenses, what might be termed a luminous mass of ribbon-like shapeextending horizontally across the optical axis AA and thus parallel tothe individual portions of the sound track that make up the sound recordon the film; the shape of this luminous mass is throughout a wide rangevirtually unaffected by the shape of the primary or incandescent massand it forms what I term for convenience a secondary source of light.This secondary source of light forms the object which is projected bythe lens or lenses carried in the member 33 (Figure 2) and by thediaphram 54 and there emanates from these lenses fill-5E and iiii5 l abeam of light which intersects the sound track (track l2 of Figure 5 ortrack 54 of Figure 6) in what is virtually a line having a lengthsubstantially equivalent to the width of the sound track and having athickness as small as less than 0.001.

Accompanying the above action, however, there is another action Whichresults from an action by the element X whereby the latter forms what Iterm for convenience a tertiary source of light. Element X, aside fromproducing the above-mentioned luminous mass or secondary source oflight, functions also to produce a general illumination of the interiorof the tube to (see Figure 2) in that light rays from the primary sourceof illumination are passed through the element X and into the tube illwholly aside from or in coaction with the illumination within the tube40 achieved by the above-mentioned luminous mass or secondary source oflight. The secondary source of light may be considered as superimposedupon or encompassed within the tertiary source of light; the former isof relatively high intensity and the latter is of lesser intensity perunit area but is of much larger area, its area being represented by theprojected area of the cylindrical surface 44 of element X as the latteris viewed from the right in Figure 2.

Light rays from this tertiary source thus formed (including orsupplemented by light rays from the secondary source) may be consideredas diffused into or as extending more or less uncontrolled into the tube40 (Figure 2) but as its light rays pass toward the right, diaphragm 55,positioned substantially at the left-hand focal point of the projectinglens or lenses 4950 and 5354, functions to determine the cross-sectionaldimension of the beam of light which emanates from this tertiary source,giving it, due to the square aperture 55" (Figure 3) a squarecrosssection. The thus square-cross-sectioned beam may now be consideredas the object so to speak which the projecting lenses 49-50 and 5354project onto the plate 20 of the photoelectric cell 9.

These lenses first converge this square-crosssectioned beam of lightfrom the tertiary source to the right-hand focal point of the lenses(coincident with the plane of the film If), Figures 1 and 4) whereuponthe beam is diverged, being projected onto the plate 26 into a verygreatly enlarged square or rectangular area which in Figure 7 I haveindicated in broken lines at 52. The lenses, however, at the same timeconverge the light rays from the secondary source of light as alreadyabove described to the same focal point, the beams from both theso-called secondary source and from the so-called tertiary source beingcoincidently converged at the same focus (in the plane of the film) tointersect the film in the line above-mentioned in connection with theaction of the lenses on the secondary source of light; I have been ableto achieve a thickness of beam where the latter intersects the film andpasses through it of as small as of 0.001".

The two beams are diversed onto the electrode 29 of the photoelectriccell [9 to illuminate the plate (disregarding for the moment anyopaqueness or approach to opaqueness in the sound rack) in the largerectangular or square area 52 of Figure 7, thus achieving a far greaterarea of illumination of the light-sensitive surface and a far greaterintensity of illumination thereof than has heretofore been achieved,with results of farreaching importance. Among the latter may at thispoint be noted the fact that the photoelectric cell is thus caused tofunction at a higher standard of operation and to have a far greateraverage current output in its output circuit than was heretoforepossible.

As now the film lil is moved as above described, the individual bar-likeportions or members of the sound track on the film I (see Figures and6), varying in their dimensions or spacings or light-transmittingproperty (according to the method employed in making the sound record)correspondingly change the amount of light striking the plate ill(Figure '7) within the rectangular area 52 and correspondingly change orvary the flow of current in the output circuit (Figure 4) of thephotoelectric cell l9 and correspondingly vary the energy input to theamplifier 25; the output of the amplifier 25 correspondingly varies andthus sufficient energy is available to actuate the loud speaker 25 atthe desired intensit l vith my system and apparatus, however, 'as abovedescribed, I have found that I am enabled far to surpass the performanceboth as to quality and efficiency and in other respects heretofore knownapparatus for sound reproduction. For example, I am enabled to achievesubstantially uniform response in the photoelectric cell circuit or insubsequent circuits to all frequencies within a range from as low as 50cycles per second to as high as 8000 cycles per second. It hasheretofore been impossible to achieve this important characteristic andin known apparatus, the response throughout the middle portion of theabove-mentioned range is substantially uniform but falls off rapidly anddetrimentally not,merely at the extreme ends of this range but alsothroughout substantial end portions as the extreme limits abovementionedare approached.

The importance of uniform frequency response is very great; uniformfrequency response means perfect faithfulness of reproduction andabsolutely naturalness of ultimate tonal character istics or qualities;sounds of the voice and of musical instruments, particularly when bothor several of each are effective, are made up of not merely given fixedfrequencies but rather of fundamental and harmonic or componentfrequencies and to lose one or more of the latter is to change thequality or naturalness of the original tone; the greater the Volume ofthe sound, and in theatres and auditoriums the volume is of greatmagnitude, the greater is the effect of the resultant distortion ordeparture from the original tone.

Furthermore, by the apparatus described above, I am enabled to obtainsuch a high standard of operation of the photoelectric cell and to makesuch efiicient and effective use thereof that the amplification requiredof the amplifier 25 (Figure 4) to produce a given volume of sound in theloud speaker 26 is but a small fraction of what is required with systemsor apparatuses heretofore known; for example, I am enabled to achievethe same required volume of sound in the loud speaker 26 with anamplification, by the amplifier 25, of only about t or 15% of theamplification necessary with certain here-tofore known apparatus. Thisimportant feature makes it possible to diminish first cost greatly inthat the amplifier need be of only much smaller capacity while theenergy consumption in and maintenance cost of the amplifier are vastlyreduced.

A significant and important feature also is the high efiiciency ofaction of the optical system a whole; for example, it is standardpractice, particularly in theatre installations to utilize a 32 wattincandescent lamp bulb having a rating of 4 amperes at 8 volts. Thisrequires the provision of storage batteries or the like to furnish thelow voltage of 8 volts and necessitates the installation ofbattery-charging equipment, not to mention the requirement ofmaintenance of such equipment as well as of the batteries themselves. Ihave achieved excellent results, such as those pointed out above, withthe use of a lamp bulb of as low as 12 watts, using a lamp having avoltage rating of 8.0 volts and a current rating of 1.40. Thus, theenergy consumption may be cut virtually in half with greater thancorresponding savings in storage battery equipment and maintenance.

I have above pointed out that the lamp socket 28 (Figure 1) does notrequire critical adjustment. With heretofore known apparatus,particularly the apparatus employing a slit, generally a slit of a widthapproximating as closely as possible 0.001", every time that a lamp bulbburns out and has to be replaced, the new lamp bulb with its socket hasto be carefully adjusted not only to get the filament centered on theoptical axis but also positioned at a critical point along the opticalaxis, and the adjustments necessary to achieve these requirements arecumbersome, tedious and time-consuming; so much so that variouscumbersome expedients, such as duplicating equipment, are resorted to inpractice. These so-called exciter lamps are intended to be of standardand uniform construction; nevertheless, even such variations ortolerances as cannot be avoided in manufacture completely disrupt theoperation of known equipment with the need for adjustments as justpointed out. With my apparatus, however, the element X inherent- 1y,because of its above-mentioned characteristics, has such a wide range ofaction with respect to the position of the luminous filament withrespect to which it acts as a secondary light source, that no suchadjustments need be made. A lamp socket with a lamp bulb of given typetherein, once adjusted or set at or even only near the optimum pointwith respect to the optical axis A-A need not thereafter be reset orreadjusted when the lamp bulb has to be replaced. Thus the burning outof a filament requires no more interruption of service than is needed tosnap the one bulb out of the socket and snap a new bulb in its place; noreadjustments are needed and it is entirely unnecessary that one beskilled in the heretofore known art of replacing and adjusting exciterlamps.

The above sets forth some of the important practical aspects of myinvention. It might be noted, however, that element X above described,as well as related coacting parts, may be varied to meet particularconditions or circumstances of use. For example, I have above pointedout that the radius of curvature of the cylindrical surface 44 ofelement X is, in the illustrative example above assumed, 4;; thiscylindrical surface, however, might be given other radii of curvature.For example, it might be given a radius of curvature of 5, or less or aradius of curvature of or more; one determining factor is the range ofspacings physically intended or available in a given sound reproducingapparatus; for example, the shorter that it is desired to make suchspacings along the optical axis A-A, as for example the spacing C ofFigure 4, the smaller should be the radius of curvature of thecylindrical surface of element X.

The optical system above described, however, may be embodied in variousother forms of which I might mention a few by way merely of example. Forexample, I improve the action and result if I make the curvature of thecurved faces 44 and 45 (Figures 8 and 8c) parabolic instead of trulycylindrical, while retaining the relation between the axes of curvature.Also, for example, I might make the curvature of the curved face 45 ofFigures 8 and 8d spherical, as indicated at 45 of Figures 9a, 9b, and90. Or I may, in any of the forms above-mentioned,

give the curved surface 44 a two-fold curvature as is shown at 4 3 inFigures 10a, 10b, and 100 from which it will be seen that the surface 44in vertical section (Figure 100) is cylindrical or parabolic incurvature while in horizontal section (as is apparent from Figure 10a)the surface thi may be given a curvature of fixed radius or of varyingradius as in a parabola.

Or I might embody the element X in the form shown in Figures 11, 11a,11b, and llc in which I have retained the curved surface 45 (which maybe modified as above described in connection with Figures 8-100) butinstead of providing a concave active surface juxtaposed to the surface65, as in these figures, I shape element X to provide a convex surface51, the convex surface also having its axis of curvature at fight-anglesto the axis of curvature of the face The surface 95, however, may begiven various shapes as above described in connection with Figures 8-100while the convex surface 5? may have its curvature of such differentforms as I have above described in connection with the concave surface44 of Figures 8l0c.

I do not desire or intend to be limited or restricted to the preciseforms above described which are set forth solely by way of example. Withsuch forms I am enabled to meet various requirements or peculiarconditions met with in practice and am enabled to achieve effectivelysuch results as I have briefly outlined hereinahcve. For example, thecurvatures of the lightreceiving surface and of the light-emittingsurface may be varied one relative to the other to better suit the shapeof any particular primary source of light that it may be desired toemploy even though any one form as already above mentioned is capable ofvery efficient and effective functioning almost irrespective of the formor shape of the initial or primary source of illumidescribed inconnection with, Figures 2 and 4,

will be clear in view of what has been set forth above. It might at thispoint, however, be noted that many features and actions of my inventionmay be achieved without the presence of, or shape of aperture in, thediaphragm 55 of Figures 2, 3, and 4, for example. I may, for example,change the shape of the aperture in the diaphragm or dispense with thediaphragm entirely. However, by dimensioning and positioning theaperture (with respect to the other elements, of course) as abovedescribed in detail in connection with Figures 2, 3, and 4, I have foundthat I am enabled to obtain best results and to achieve a heretoforeunachieved ratio of energy output of the photoelectric cell to the lighteffective in the optical system.

I have earlier hereinabove mentioned that the optical system of Figure 2is sealed; to effect this sealing dependably I prefer to employ, wherethreaded parts are used, a small pitch of thread and to seal thethreaded parts as well as any of the glass-and-metal joints with asuitable cement. I have found a satisfactory cement to comprise amixture of zinc oxide and water glass or a mixture of finely powderedlitharge and glycerin-e, for ealing such joints. Such cements are notaffected by heat, moisture, oil, or vapors thereof and thus theeffective glass parts of the optical system are dependably sealedagainst such foreign matters as these and are dependably kept clean.Thus, I eliminate the need for having to clean these parts or to arrangethem so that they may be easily disassembled for cleaning purposes.

From the foregoing I believe the practice of my invention in so far assound reproduction is concerned will be clear. As for sound recording,what I have stated above makes clear how I am enabled to achieve, at theintersection of the beam of light with the film, a straight lineextending crosswise of the sound track but of very minute dimension; Ihave above pointed out that I can achieve a thickness of beam at thisintersection of 0.0003". This is an important desideratum in that I amenabled to cut the higher frequency film records of sound with suchnicety and precision that virtually none of the important contributionof the high frequencies to the quality and naturalness of sound is lost.By means of my invention, moreover, I am enabled to record sound on filmwith greater faithfulness and naturalness than has heretofore beenpossible and in Figure 12 I have diagrammatically indicated one ofvarious possible embodiments of sound recording apparatus embodying myinvention.

Referring then to Figure 12, I have shown at 58 the film on the soundtrack of which a film record like that of Figure 5 is to be made; thefilm 58 is guided and driven along a predetermined path or in a fixedplane by any suitable mechanism which may include driving and drivensprockets 59-69. At 5! I have indicated a suitable sound responsivedevice suitably related to a suitable means for affecting the beam oflight which I project upon the sound track of film 58. Conveniently, thedevice 6| takes the form of a microphone or the like adapted to vary theoutput of a suitable source of current 62 in accordance with thefrequency of the sound striking the device 6!, whereupon a suitableamplifier 63 suitably amplifies the resultant audio frequency currentsin order to correspondingly affect the electrodes of a suitable Kerrcell suitably related to suitable Nicol prisms, all of which arediagrammatically indicated at 6 1, conductors 55 and 5B connecting theelectrodes into the output circuit of the amplifier 83.

The Kerr cell, interposed between two Nicol prisms is, with the latter,inserted in the path of light originating from a suitable primary source61 and directed to and upon the sound track of the film 58.

Interposed between the source of light Si and the Kerr cell and Nicolprism assembly, is a light tube diagrammatically indicated at ME] and embodying therein a light-ray controlling system substantially like thatabove described in connection with Figures 2 and 3.

The light tube MD of Figure 12 has mounted therein element X and nearestthe primary source of light 61, thus to form secondary and tertiarysources of light as was already above described in detail. To the leftof element X is a diaphragm 55 with a square aperture i55a therein andto the left of the diaphragm are achromatic projecting lenses M9 M9 andl53-l54 substantially like lenses it--59 and Sit-54 of Figure 2.

The rectangularly-cross-sectione-d beam of light then passes through theKerr cell and Nicol r assembly where its intensity is v cordance withthe audio frequency current output of the amplifier E3, all while thefilm 53 is being moved at a suitable speed, whereupon the beam of light,now varying in intensity at an audio frequency rate, emanating from theassembly 64 is converged by any suitable lens or lens system $8 onto thesound track of film 58, thus to form a sound record like that shown inFigure 5.

With this system and method of sound recording, it being understood thatI may employ other means, such as a vibrating mirror, for affecting atan audio frequency rate the actinic action of the light on the film, Iam enabled to use virtually any shape of initial light source 61 in viewof the action th reon of the element X as will now be clear in view ofWhat I have set forth in detail in connection with the soundreproduction. Moreover, the so-called image (the intersection in a lineof the light beam with the sound track on the film 53) is, like theso-called object (the secondary and tertiary sources of light)accurately and geometrically rectilinear in its boundaries; thischaracteristic, true of my method and apparatus for sound recording aswell as of my method and apparatus for sound reproduction, will bebetter understood when I point out that, where a minutely dimensionedslit is employed the image and/or the object are not rectilinearlybounded but are bounded by irregular zigzag or saw-toothed lines; thelatter effects are due to the fact that it is impossible physically toachieve light-bounding surfaces so smooth that they will not provide amultitude of light-reflecting or light-affecting minute surfaces ofvarious angles to each other, being oftentimesaccompanied by a prismaticaction in breaking up white light into various component colors.

The resultant stray light and the resultant irregularly shaped beamprevent the achievement of precision of action on the film, either inreproduction or recording. These detrimental ac.- tions, however, areentirely absent with my systom and apparatus in which, virtually nomatter what the shape of the incandescent filament or other lightsource, I achieve, without mechanical restriction or obstruction, across-section of beam of light that is bounded by geometrically perfectlines, free from such irregularities and actions as have just beenmentioned.

This characteristic, therefore, makes it possible for to record withperfect precision and this is ..rticularly important where the higherfrequencies, such as 8060 cycles per second or above ar concerned. Acontributing factor to faithfulness recording and to faithfulness ofreproduction is also the small thickness of beam which I am enabled toachieve, where it intersects the film.

From the foregoing, the practicing of my invention, I believe, will nowbe clear and it will be seen that I have provided a method and appaforrecording and reproducing sound in oh the various objects hereinbeforeset forth a" well as others, together with many thoroughly cticaladvantages are successfully achieved. I wish again topoint out theuniformity of frequency response. which I have been able to achieve; ii,for example, in the reproduction of sound from the film record as abovedescribed, apparatus is analyzed and tested in actual operation, it willbe found that, due to the various characteristics and coactions of thevarious coacting parts, the energy or power output and hence the volumeof ultimately reproduced sound remain substantially constant over arange of frequencies from at least 50 cycles per second to over 8000cycles per second; this is a performance which it has heretofore inpractice been impossible to achieve though many attempts have been madeto achieve this result. Certain important effects of this result uponthe quality or naturalness of reproduction I have already hereinabovementioned.

Furthermore, the apparatus is characterized by highly desirablesimplicity of control or operation, an example of which I have alreadymentioned above in connection with replacement of a burnt-out exciterlamp. Furthermore, the over-all efficiency is of heretofore unsurpassedmagnitude as will be clear from even only a brief consideration of thesmall energy input to the eXciter lamp and a comparison thereof with theexceedingly small amount of amplification of the photoelectric celloutput to give a volume of sound comparable to or even in excess ofheretofore known practical methods.

As many possible embodiments may be made of the mechanical features ofthe above invention and as the art herein described might be varied invarious parts, all without departing from the scope f the invention, itis to be understood that all matter hereinabove set forth or shown inthe accompanying drawings is to be interpreted as illustrative and notin a limiting sense.

1. In apparatus of the character described, in combination, means havinga light-sensitive surface, a source of light, a film having a soundrecord thereon, means for guiding and moving said film along a. pathinterposed between said source of light and said surface, and means forcausing light from said source to intersect said sound record in astraight line and to strike said surface a iarge rectangular area, saidmeans comprising light-ray controlling means for converting said sourceof light, irrespective of its shape, into a secondary source of lightthat is relatively thin in the direction of the length of the soundrecord and relatively elongated in a direction transversely of the soundrecord, said ray-controlling means having the characteristic ofconverging light rays from said source of light in said firstmentioneddirection and of diverging light rays from said source in saidsecond-mentioned direction, projecting lens means interposed betweensaid secondary light source and said film, said film being at one focalpoint of said lens means, and a diaphragm intermediate of said secondarysource of light and said projecting lens means, said diaphragm having asquare aperture and being spaced along the optical axis a substantialdis tance from said secondary source of light and being positioned atthe other focal point of said projecting lens means.

2. In apparatus of the character described, in combination, means havinga light-sensitive surface, a source of light, a f lm having a soundrecord thereon, means for guiding and moving said film along a pathinterposed between said source of light and said surface, and means forcausing light from said source to intersect said sound record in astraight line and to strike said surface in a large area, said meanscomprising light-ray controlling means for converting said source oflight, irrespective of its shape, into a secondary source of light thatis relatively thin in the direction of the length of the sound recordand relatively elongated in a direction transversely of the sound r rd,said ray--controlling means having the characteristic of converginglight rays from said source of light in said first-mentioned directionof diverging light rays from said source in said second-mentioneddirection. said lightray controlling means including a glass elementbounded by two substantially cylindrical surfaces, one of which is ofrelatively large radius and has an axis substantially parallel to saidfirst-mentioned direction and the other of which has a relatively smallradius of curvature about an axis at right angles to saidfirst-mentioned axis, and means interposed between said element and saidfilm for projecting the secondary light source through said sound recordand onto said lightsensitive surface, said sound record beingsubstantially at the focus of said projecting means.

3. In an apparatus for recording sound on film, in combination, asensitized film, means for moving and guiding said film along a certainpath, a source of light, and means for causing light from said source tostrike said film in a thin straight line, said last-mentioned meanscomprising light-ray controlling means for converting said source oflight, irrespective of its shape, into a secondary source of light thatis relatively thin in the direction of the path of movement of the filmand relatively elongated in a direction transversely of said path ofmovement, said ray-controlling means comprising a glass element boundedby two substantially cylindrical surfaces, one of which is of relativelylarge radius and has an axis substantially parallel to saidfirst-mentioned direction and the other of which has a relatively smallradius of curvature about an axis at right angles to saidfirst-mentioned axis and having the characteristic of converging lightrays from said source of light in said first-mentioned direction and ofdiverging light rays from said source in said second-mentioneddirection, and means responsive to sound for effecting an audiofrequency change in a characteristic of the beam of light striking saidmoving film.

4. In an apparatus like that claimed in claim 3, in which radius ofcurvature of one of the cylindrical surfaces of the glass element is onthe order of 0.125" and the radius of curvature of the other is on theorder of 0.75.

5. In an apparatus like that claimed in claim 3 in which that surface ofsaid glass element that is nearest the light source is convex and oflarge curvature about an axis parallel to the direction of movement ofthe film and the surface nearest the film is of a curvature about anaxis at right angles to said first-mentioned axis.

6. An apparatus like that claimed in claim 2 in which that surface ofthe glass element which is nearest the film is concave.

'7. An apparatus like that claimed in claim 2 in which that surface ofthe glass element which is nearest the film is convex.

8. An apparatus like that claimed in claim 2 in which the curvature ofat least one of the surfaces of the glass element is parabolic.

9. An apparatus like that claimed in claim 2 in which the surface of theglass element nearest the source of light is spherical.

10. An apparatus like that claimed in claim 2 in which the surface ofthe glass element that is nearest the film also has a curvature about anaxis parallel to the path of movement of the film.

11. An apparatus like that claimed in claim 3 in which thesound-responsive means includes a Kerr cell and Nicol prisms betweenwhich and the secondary source of light there is interposed a diaphragmhaving an aperture therein that is rectangular for controlling thecross-section of the beam of light upon which the Nicol prisms and Kerrcell act.

12. An apparatus like that claimed in claim 3 in which there is provideda diaphragm having a rectangular aperture positioned in the path oflight rays originating in said secondary source of light for giving thebeam of light a rectangular cross-section.

13. An apparatus like that claimed in claim 2 in which the twosubstantially cylindrical surfaces are spaced in the direction oflight-projection and have radii of curvature on the order of 0.125 and0.75" and in which the glass element is made of crown glass having anaverage index of refraction of 1.52 and a dispersion factor for theD-line of 64.0.

14. In apparatus of the character described, in combination, meanshaving a light-sensitive surface, a source of light, a film having asound record thereon, means for guiding and moving said film along apath interposed between said source of light and said surface, and meansfor causing light from said source to intersect said sound record in astraight line and to strike said surface in a large area, said meanscomprising light-ray controlling means which include a glass memberbounded by two surfaces spaced in the direction of light-projection, thesurface of said glass member that is nearest the film having a curvatureabout an axis parallel to the path of movement of the film and its othersurface being shaped to cause said member to diverge light rays in adirection transversely to the path of movement of the film.

15. In apparatus of the character described,

in combination, means having a light-sensitive surface, a source oflight, a film having a sound record thereon, means for guiding andmoving said film along a path interposed between said source of lightand said surface, and means for causing light from said source tointersect said sound record in a straight line and to strike saidsurface in a large area, said means comprising light-ray controllingmeans which include a glass member bounded by two surfaces spaced in thedirection of light-projection, the surface of said glass member that isnearest the film having a radius of curvature on the order of 0.125, thecurvature being about an axis parallel to the path of movement of thefilm and its other surface being shaped to cause said member to divergelight rays in a direction transversely to the path of movement of thefilm, said glass member having an average index of refraction on theorder of 1.52 and a dispersion factor for the D- line on the order of64.0.

16. In an apparatus like that claimed in claim 15 in which there is atube-like member in which said glass member is mounted, said tube-likemember being positioned between the source of light and the film, saidglass member having ex tensions or portions such that it is peripherallysubstantially circular for reception within said tube-like member, saidextensions or portions of said glass member being opaque,

17. An apparatus like that claimed in claim 15 in which the spacingbetween the source of light and said glass member is on the order of1.25" and in which the spacing from the glass member to the film is onthe order of 2.250".

PAUL SAFRANSKI.

CERTIFICATE or COBRECTION.

Patent NO. 2,037,73 April 21 1956.

PAUL SAFRAI'SK It is hereby certified. that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 9, first 1 4 5 respectively, for the reference numcolumn,lines 59 and 44-, cieims i eral "5" read 2; and that tLe said LettersPatent corrections therein that the same may conform the record of thecase in the Patent Office Signed and sealed. this 4th of August, A. Do

should be with these Henry Van Arsdale (Seal) Acting Commissioner ofPatents.

CERTIFICATE OF CORRECTION.

Patent NO. 2,057,759. April 21, 1956.

PAUL SAFRANSKI It is hereby certified that error appears in the printedspecification oi" the above numbered patent requiring correction asfollows: Page 9, first column, lines 59 and 44., claims 4 5respectively, for the reference numeral "5" read 2; and that the saidLetters Patent should. be read with these corrections therein that thesame may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of August, A. D. 1936.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

